[IPV6]: ROUTE: Add support for Router Preference (RFC4191).

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/icmpv6.h b/include/linux/icmpv6.h
index 0cf6c8b..c771a7d 100644
--- a/include/linux/icmpv6.h
+++ b/include/linux/icmpv6.h
@@ -40,14 +40,16 @@
                 struct icmpv6_nd_ra {
 			__u8		hop_limit;
 #if defined(__LITTLE_ENDIAN_BITFIELD)
-			__u8		reserved:6,
+			__u8		reserved:4,
+					router_pref:2,
 					other:1,
 					managed:1;
 
 #elif defined(__BIG_ENDIAN_BITFIELD)
 			__u8		managed:1,
 					other:1,
-					reserved:6;
+					router_pref:2,
+					reserved:4;
 #else
 #error	"Please fix <asm/byteorder.h>"
 #endif
@@ -70,8 +72,13 @@
 #define icmp6_addrconf_managed	icmp6_dataun.u_nd_ra.managed
 #define icmp6_addrconf_other	icmp6_dataun.u_nd_ra.other
 #define icmp6_rt_lifetime	icmp6_dataun.u_nd_ra.rt_lifetime
+#define icmp6_router_pref	icmp6_dataun.u_nd_ra.router_pref
 };
 
+#define ICMPV6_ROUTER_PREF_LOW		0x3
+#define ICMPV6_ROUTER_PREF_MEDIUM	0x0
+#define ICMPV6_ROUTER_PREF_HIGH		0x1
+#define ICMPV6_ROUTER_PREF_INVALID	0x2
 
 #define ICMPV6_DEST_UNREACH		1
 #define ICMPV6_PKT_TOOBIG		2
diff --git a/include/linux/ipv6_route.h b/include/linux/ipv6_route.h
index d7c41d1..f4b085c 100644
--- a/include/linux/ipv6_route.h
+++ b/include/linux/ipv6_route.h
@@ -27,8 +27,16 @@
 #define RTF_FLOW	0x02000000	/* flow significant route	*/
 #define RTF_POLICY	0x04000000	/* policy route			*/
 
+#define RTF_PREF(pref)	((pref) << 27)
+#define RTF_PREF_MASK	0x18000000
+
 #define RTF_LOCAL	0x80000000
 
+#ifdef __KERNEL__
+#define IPV6_EXTRACT_PREF(flag)	(((flag) & RTF_PREF_MASK) >> 27)
+#define IPV6_DECODE_PREF(pref)	((pref) ^ 2)	/* 1:low,2:med,3:high */
+#endif
+
 struct in6_rtmsg {
 	struct in6_addr		rtmsg_dst;
 	struct in6_addr		rtmsg_src;